Within wireless communications networks, such as global system for mobile communication (GSM) networks, universal mobile telecommunications system (UMTS) networks, general packet radio service (GPRS) networks, IS-41 networks, personal communications system (PCS) networks, etc., signaling messages are used to convey location information associated with mobile subscribers. Both implicit and explicit location information may be communicated via such signaling messages. For example, in a typical GSM network, a mobile application part (MAP) UpdateLocation message is used to convey location information to a mobile subscriber's home location register (HLR). In this case, the location information may be a serving mobile switching center (MSC) address and/or a serving visitor location register (VLR) identifier.
Advances in satellite-based global positioning system (GPS), timing advance (TA), and terrestrial-based enhanced observed time difference (E-OTD) position fixing technology enable a precise determination of the geographic position (e.g., latitude and longitude) of a mobile subscriber. As geographic location services are deployed within wireless communications networks, such positional information may be stored in network elements and delivered to nodes in the network using signaling messages. Such information may be stored in HLRs, VLRs, and special purpose mobile subscriber location databases. One example of a special purpose mobile subscriber location database is the mobile location center (MLC) proposed by the European Telecommunications Standards Institute (ETSI). In particular, ETSI has defined a signaling protocol for communicating mobile subscriber positional information to and from an MLC. This signaling protocol is referred to as the radio resource location services protocol (RRLP) and defines signaling messages communicated between a mobile station and a serving MLC related to a mobile subscriber's location. A detailed description of the RRLP protocol is found in 3GPP TS 44.031 v4.2.0 (2001-09) 3rd Generation Partnership Project; Technical Specification Group GSM Edge Radio Access Network; Location Services (LCS); Mobile Station (MS)—Serving Mobile Location Centre (SMLC) Radio Resource LCS Protocol (RRLP) (Release 4), the disclosure of which is incorporated herein by reference in its entirety.
FIG. 1 illustrates an exemplary wireless communications network, generally indicated by reference numeral 100. In FIG. 1, wireless communications network 100 includes a mobile station (MS) 110, a base station (BS) 112, a mobile switching center (MSC) co-located with a VLR 114, a signaling network 116, and an MLC 118. As indicated in FIG. 1, signaling messages employing the RRLP protocol may be communicated between MLC 118 and MS 110 via signaling network 116. The particular RRLP messaging transaction illustrated in FIG. 1 includes an RRLP_MeasurePositionRequest message originated by MLC 118. The purpose of this message is to request that mobile station 110 provide position information. The RRLP_Measure_Position Request message is routed via signaling network 116, MSC/VLR 114, and BS 112 to destination MS 110. MS 110, in turn, takes a position measurement and returns the position information via an RRLP_MeasurePositionResponse message. The RRLP_MeasurePositionResponse message is routed to MLC 118 via signaling network 116. MLC 118 receives the message, parses out the position information, and stores the information in a database local to MLC 118.
While the RRLP protocol specification describes messaging for requesting mobile subscriber location information from a mobile station or handset and for communicating that information to an MLC, there is no mechanism described therein for placing a specific mobile subscriber under surveillance or for automatically notifying an enforcement agency of the location of mobile subscriber under surveillance. Moreover, conventional telephony-based surveillance techniques have resulted in delays in call setup that may inform the mobile subscriber that he or she is under surveillance. Once the mobile subscriber knows he or she is under surveillance, the surveillance is of little value to the enforcement or security agency performing the surveillance. Accordingly, there exists a long-felt need for improved methods and systems for mobile subscriber surveillance.